The present invention relates to the field of signal coupling in integrated circuits and printed circuit boards.
Modern electronic devices have gotten steadily smaller with advances in Integrated Circuit (IC) design and advances in packaging. More and more functions have been pressed into smaller and smaller appliances. This phenomenon is most apparent in the realm of portable telephones.
In many electronic devices, and especially in those such as portable phones that require analog power amplification, there are occasions in which one circuit requires an indication or quantification of a signal or current flow in a different circuit. While there are times the two circuits are incompatible and incapable of direct connection, a more important consideration is that the sensing circuit not degrade or otherwise influence the signal being sensed.
There are devices in existence which provide the transfer of current or frequency information between circuits, specifically between conductors, without a direct connection being required. Optical couplers, for example, utilize a combination LED/photocell to non-electrically transfer information between circuits. Optical coupling, however, requires additional components: the LED and photocell and their supporting circuitry with their attendant complexity and size. Inductive couplers also do not require a direct connection but lack the ability to sense current direction.
Electromagnetic coupling, where a current fluctuation in a transmission line causes an analogous current fluctuation in an adjacent line, has both inductive and capacitive components. It can be used to transfer information between two circuits without a direct connection. However, typical electromagnetic coupling requires either very large currents in the xe2x80x9csendingxe2x80x9d conductor in order to provide a readable signal in a xe2x80x9creceivingxe2x80x9d conductor or very close proximity of the xe2x80x9csenderxe2x80x9d and xe2x80x9creceiverxe2x80x9d. While electromagnetic coupling provides current, frequency and direction information, achieving the proximities required to employ electromagnetic coupling in low power circuits has been somewhat impractical. Additionally, even at relatively low currents, high RF frequencies radiate electromagnetic fields (EMFs) that induce signals in areas where they are not desirable and receiving conductors must be very sensitive to correctly read the emitted EMF. To counteract that, a coupler must be properly shielded.
One means used to form a coupler is to position two transmission lines and associated dielectric layers in a single IC. This requires a complex, specially fabricated, IC that limits the application of the coupling and also requires the transfer of the relatively high power, high frequency, sending current from the printed circuit board (PCB) onto the IC. The limited vertical dimensions available on a typical IC also limits the range of achievable impedances, further limiting the sensitivity and application of integrated couplers.
Another means is by building a difficult-to-manufacture sandwich of conductors, dielectrics and shielding groundplanes, and installing the assembly on a PCB. This method, though effective at coupling, entails the additional disadvantage of using up a large amount of valuable PCB space.
What is needed, then, is a means of reliably employing directionally sensing electromagnetic coupling in low power circuits in a small package. Furthermore, such a means must minimize the number of devices that must handle large currents and must minimize additional complexity and cost.
Presented herein is a means of reliably employing directionally sensing electromagnetic coupling in low power circuits in a small package. The means provides minimal additional complexity and cost and yet provides the advantages of not requiring a transfer of a large current and/or high frequency signals to a chip and of using a miniscule amount of PCB real estate.
The present invention relates to a method for providing non-contact power/current sensing in an electronic circuit. Specifically, the method provides an electronic coupler in the form of an integrated circuit microstrip mounted in close proximity to a current-carrying microstrip on a printed circuit board. The integrated circuit is mounted on and electronically coupled to electronic components of said printed circuit board with the microstrip on the printed circuit board side of the integrated circuit substrate, and the integrated circuit microstrip is positioned in such a way as to effect electromagnetic coupling to an electronic trace on the printed circuit board.
Embodiments of the present invention disclose a method for providing an electronic coupler which comprises a printed circuit board and an integrated circuit which is mounted on and electronically coupled to electronic components on the printed circuit board. The integrated circuit is positioned in such a way as that it electromagnetically couples to an electronic trace on the printed circuit board.